The prevalence of ZnT8Ab varied between 58% [11] and 83% [7] in newly diagnosed T1D patients with a

general lower prevalence in the Chinese population (24%) [12]. Consistently, ZnT8R autoantibodies (ZnT8RAb) (50–54%) appear to be more frequent than ZnT8W autoantibodies (ZnT8WAb) (41–50%) [13-15] and ZnT8Q autoantibodies (ZnT8QAb) (32–36%) [14, 15] in White people. Although ZnT8QAb are found in combination with ZnT8RAb or ZnT8WAb, it selleck is rare to find patients who have only ZnT8QAb and no other islet autoantibody [16]. Importantly, ZnT8Ab have been found to react differently to the ZnT8 cytoplasmic fragment used for autoantibody detection dependent on the amino acid at position 325 [13]. The amino acid at position 325 in the COOH-terminal part of ZnT8 is controlled by the single nucleotide polymorphism (SNP) rs13266634 in the gene of ZnT8, SLC30A8 [17]. This genetic Erlotinib cost polymorphism causes an amino acid change in position 325 from arginine (CGG) present

in 69% compared to 31% for tryptophan (TGG) in healthy controls [18] and was not found to be associated with T1D in the genetic consortium (GM) genome-wide association scanning [19]. Despite the absence of an association with T1D, several authors have independently reported a correlation between the rs13266634 genotype and the autoantibody specificity of ZnT8RAb and ZnT8WAb [13, 20] [9, 21]. T1D patients with the C allele more often than expected had ZnT8RAb, and patients with the T allele had ZnT8WAb. As 30–44% of ZnT8Ab-positive subjects react with all three variants [13], that is, despite that subject is homozygous for R/R, there may still be autoantibodies that react with ZnT8W [15]. The character of the residue 325 in Farnesyltransferase ZnT8 was thought to represent a conformational epitope [22]. However, the epitope-specific reactivity to the ZnT8 268–369 in vitro transcription translation product is poorly investigated. The aims of the present study were therefore to 1) determine the immunogenicity of 15-mer short ZnT8 (318–331) peptides in mice with either R or W at position 325; 2) test the

ability of these short ZnT8 peptides to compete with radiolabelled (ZnT8 268–369) long proteins in binding to patient sera specific for either ZnT8RAb or ZnT8WAb; and 3) test the ability of the unlabelled long ZnT8 (268–369) proteins to compete with radiolabelled long ZnT8 (268–369) proteins in binding to patient sera specific for either ZnT8RAb or ZnT8WAb. Fifteen-mer peptides (short) of ZnT8R, ZnT8W and ZnT8Q (aa 318–331) covering sequences NH2-CHVATAASRDSQVVR-COOH) with R, W or Q, respectively, in the aa position 325 (Fig. 1) were synthesized by a standard Solid-phase peptide synthesis (SPPS) with 9-fluorenylmethyloxycarbonyl group (Fmoc) and determined by mass-spectrometry (MS) at Innovagen AB, Lund, Sweden. AB.